In medicine systems (robot systems) for (manual or preprogrammed) control of intracorporeal objects by means of extracorporeally generated magnetic fields are known. Intracorporeal objects, for instance endoscopic capsules, probes or catheters, to this effect have an element adapted to be influenced by magnetic fields, e.g. a permanent magnet which is mounted in the object. The orientation and/or positioning of the intracorporeal objects can be controlled by extracorporeally generated magnetic fields. For providing extracorporeal magnetic fields likewise systems for generating electromagnetic gradient fields, for instance in the form of magnetic resonance imaging scanners, electromagnetic spot fields, e.g. by a solenoid in compact design, as well as systems including a permanent magnet are known.
Systems for generating electromagnetic gradient fields, for instance according to the design of magnetic resonance imaging scanners, have the drawback that, compared to other electrical equipment common in medical practices or in hospitals, these apparatuses have a very high power requirement and, due to their design, are very large and heavy compared to technical apparatuses otherwise common in medical practices or hospitals. Advantages of the systems according to the design of magnetic resonance imaging scanners are, however, that the gradient field can be set to be finely adjusted and reproducible at the location of the intracorporeal objects for controlling the same and that a risk for the patient by movable components can be largely excluded, because the movable parts are provided inside a rigid shell statically surrounding the patient.
Hereinafter, by the term “magnetic field generator of compact design” those apparatuses are to be understood which generate a magnetic field extending in space around the apparatus so that the apparatus is provided in the center of the generated magnetic field. In particular, the range of use of those magnetic fields generated by magnetic field generators of compact design extends in the spatial environment of said magnetic field generators. In contrast to that are generators of a gradient field, for instance according to the design of a magnetic resonance imaging scanner whose range of use extends to the interior of an annular apparatus into which a patient has to be moved, i.e. the useful magnetic field is not intended to surround the magnetic field generator but to extend in a direction (radially inwards of the annular apparatus) away from the same. Magnetic field generators of compact design can consist, for example, of one or more solenoids or one or more permanent magnets or of combinations of the two.
The term “force” as generally used hereinafter can describe a mechanical force or a torque.
The use of magnetic field generators of compact design according to the above definition has the advantage that the apparatuses have a similar power requirement compared to other electrical equipment common in medical practices or hospitals and, due to their design, have a similar size and weight compared to technical apparatuses otherwise common in medical practices or hospitals. That is, they are basically suited also for mobile use in a practice or hospital with normal effort. However, a drawback of the use of magnetic field generators of compact design for the control of an intracorporeal object resides in the fact that for adjusting the magnetic field at the location of the intracorporeal object the position and orientation of the magnetic field generator of compact design (e.g. permanent magnet or solenoid) in space is required, i.e. the magnetic field generator of compact design must be moved in space relative to a patient. According to current prior art, the orientation of the magnetic field generator of compact design in space is achieved either manually or by actuated (motor-driven) robotic devices, i.e. magnetic guiding devices as they are called. Another drawback of magnetic field generators of compact design is that the intensity of the magnetic field in the range of use is strongly reduced with an increasing distance from the magnetic field generator. For this reason it is advantageous and possibly also necessary to position the magnetic field generators of compact design as closely as possible to the intracorporeal object to be controlled so that an impact of the magnetic field on the intracorporeal object sufficient for the control of the intracorporeal object is provided.
The manually guided orientation of the magnetic field generator of compact design has the advantage that the structure may exhibit minimum complexity. Embodiments include the movement of a hand-held permanent magnet as well as manually guided passive, i.e. not actuated assistance systems for compensating the weight of the magnetic field generator of compact design. It is a further advantage that the controlling person gets a permanent information feedback on the motion parameters and especially collisions with and action of force upon a patient's body by the manual orientation of the magnetic field generator of compact design by at least his/her haptic sense and that thus actions endangering the patient can be avoided when orientating the magnetic field generator of compact design. The manually guided orientation of the magnetic field generator of compact design in space has the drawback, however, that the controlling effect of orientating motions of the magnetic field generator of compact design on the orientation of the intracorporeal object are not intuitively predictable, because the controlling person has no direct visual connection to the intracorporeal object and thus obtains no information about the current position and orientation of the same. That is to say, no direct information about the current position and orientation of the intracorporeal object can be conveyed to the controlling person via the magnetic field generator, which would be analogous to a visual flight at night. It is clear that a guiding method based on the afore-described devices is feasible only with very much practice and presumably with insufficient results. This fact is described in detail in EP 2 347 699 A1, which is incorporated by reference in its entirety, for instance.
The robot-guided orientation of the magnetic field generator of compact design in space on the other hand has the advantage that by direct information feedback between the intracorporeal object and the robotic device controlling the magnetic field generator of compact design (robot arm) a control of the position and the orientation of the intracorporeal object intuitive and predictable to the controlling person can be obtained. The principle of such information feedback is disclosed in the afore-mentioned EP 2 347 699 A1 so that in this context the respective publication can be referred to for complete understanding of the present technical teaching.
A robot-guided orientation of the magnetic field generator of compact design in space has the drawback, however, that the apparatus for robot-guided orientation of the magnetic field generator of compact design basically can perform also those movements which might result in a collision with and without action of force on a patient's body and thus in actions endangering the patient or the controlling person upon his/her body. In other words, robots of conventional conception are easily capable of fatally injuring a person or damaging neighboring objects in the case of a wrong movement so that typically a safety area has to be closed off in the field of motion of the respective robot.
As explained already in the foregoing, it is of advantage to position the magnetic field generator of compact design as closely as possible to the intracorporeal object to be controlled so as to exert sufficient magnetic attraction on the object. It can even be of advantage to press the magnetic field generator of compact design with a defined force onto a patient's body so as to form an indentation of the body for example in the abdominal region which enables the magnetic field generator of compact design to be positioned even more closely to the intracorporeal object to be controlled. In such situation movements of the magnetic field generator can be directly (mechanically) transmitted to a patient's body both for positioning and orientation of the magnetic field generator of compact design and can result in impacts on the patient's body endangering the patient. It is also obvious that safety areas in the conventional meaning are not applicable in this case.
It is technically possible to establish so called virtual barriers so as to prevent collisions or excessive force actions on the patient's body. Virtual barriers are limits deposited in the software of the control system of the device for the robot-guided orientation of the magnetic field generator of compact design in the form of space coordinates or actuator positions that are not exceeded in the case of intended function of the device, i.e. there is basically the possibility of virtually establishing the afore-mentioned safety area by programming measures. However, it is a drawback of this technical measure that the individual anatomic facts of patients (stout, slim, male, female etc.) cannot be taken into account. Consequently, the best possible approximation of the magnetic field generator of compact design to the intracorporeal object to be controlled is no longer given in each case. A further drawback of virtual barriers consists in the fact that they are implemented on a software level and thus further measures have to be taken on a software level for detecting malfunctions. Malfunctions possibly cannot be detected or mastered early enough by a user who is not technically versed.
In contrast to a virtual barrier according to the afore-mentioned definition, also a patient's body to be examined can be separated by a physically existent rigid barrier such as a cage from the device for robot-guided orientation of the magnetic field generator of compact design so as to eliminate the risk of impacts on the patient's body endangering the patient (crash protection). Drawbacks of this technical measure are, however, that the rigid barrier itself requires some space which is no longer available to the device for robot-guided orientation of the magnetic field generator of compact design and said barrier cannot take the individual anatomic facts of patients into account, either, unless the rigid physical barrier includes adjusting options so as to at least approach the same to the patient's anatomy. Thus the action of force on the patient's body advantageous to the approach of the magnetic field generator of compact design is no longer possible, i.e. by this technical solution of disposing a physical barrier the best possible approach of the magnetic field generator of compact design to the intracorporeal object to be controlled is no longer given (in each case), either.
Especially when applying actuated (motor-driven) systems in medical practice or hospital, it is necessary to meet strict safety requirements on the basis of risk disclosures. Risks for patients by the robot-guided orientation of a magnetic field generator of compact design inter alia result from the movements of the device for positioning and/or orientation of the magnetic field generator of compact design that may entail collisions with or without action of force upon the patient's body and thus impacts on the patient's body endangering the patient.
To make things worse, on particular conditions predefined collisions with or without action of force upon the patient's body can even be advantageous, for example in order to move the magnetic field generator of compact design as closely as possible to the intracorporeal object to be controlled, as this has already been indicated before. In this case a sensory feedback of the action of force of the device for the robot-guided orientation of the magnetic field generator of compact design on the patient's body is of advantage/necessary so as to specifically produce and also restrict the action of force. In this way, the action of force upon the patient's body can be kept within a range that does not endanger the patient. However, the problem in this case is that sensors for detecting the situation of collision may fail or provide wrong measuring results, the latter malfunction possibly being not realized not at all or too late (for the patient).
What is moreover crucial to a risk disclosure of such device is the question which actuated (motor-generated) maximum force can be exerted on the patient in the case of malfunction. For instance, a malfunction of a sensor can lead to the fact that the device increases the action of force on the patient's body beyond the range which does not endanger the patient, viz. to a range which endangers the patient. For this, the actuators or motor drives such as electric motors, piezo drives, hydraulic or pneumatic control pistons, electromagnetic drives etc. used in the device are required to be able to/have to generate a greater force than provided in the intended function.
The robotic guide of a magnetic field generator of compact design requires orientation of the magnetic field generator of compact design with (a maximum of) five degrees of freedom of motion. Said five degrees of freedom are translational motions along the three spatial axes disposed at right angles with each other as well as the rotation about those spatial axes that are normal to each other and preferably normal to the axis of polarization of the magnetic field generated by the magnetic field generator of compact design and hereinafter are referred to as pitching and yawing motion. The axis of polarization is co-linear with respect to the connecting line between the north and south magnetic poles of the magnetic field generator of compact design. Since rotation of the magnetic field generator of compact design about said polarization axis of the magnetic field (currently defined as “rolling motion”) does not result in a change of the magnetic field in space, this orientation of the magnetic field generator of compact design by the device for robot guiding thereof is not expedient or is technically meaningless and thus superfluous.
Devices for robot-guided orientation of a magnetic field generator of compact design preferably are robot arms or extensions. Commercially available robot arms known today are largely used in automation engineering and are optimized to high travel rates, high precision as well as variability in tracking and load bearing.
In the robot-guided orientation of a magnetic field generator of compact design for the control of intracorporeal objects, on the other hand, the usual travel velocities are definitely lower than the travel velocities common in automation engineering. Whereas in automation engineering travel velocities are within the magnitude of up to 10 meters per second, in the use of a device for robot-guided orientation of a magnetic field generator of compact design according to aspects of the present invention definitely lower travel velocities are required, for example within the range of up to 0.1 meter per second. The drawback of commercially available robot arms known today for automation engineering resides in the fact that the actuating elements are designed for high velocities and therefore can release great forces. Moreover, robots of this species frequently have to carry and move heavy loads (including the dead weight of the robot arms) so that great driving forces and/or torques are required to move the robot arms. For this reason, in automation engineering those robot arms are used exclusively within rigid barriers as explained already in the foregoing. When used for a robot-guided orientation of a magnetic field generator of compact design, controlling errors or malfunctions therefore can lead to impacts on the patient's body endangering the patient.
However, in the robot-guided orientation of a magnetic field generator of compact design for the control of intracorporeal objects according to the aspects of present invention requirements to the precision and the variability of tracking and load bearing are definitely lower than usual today in automation engineering. For accurately orientating an intracorporeal object precision of the movement of the extracorporeal magnetic field generator of compact design within the range of millimeters up to one centimeter is completely sufficient, because the dislocation of the magnetic field generator of compact design within this range results in an only insignificant change of the magnetic field at the location of the intracorporeal object. Furthermore, in the robot-guided orientation of a magnetic field generator of compact design for the control of intracorporeal objects the requirements to variability of tracking are restricted due to the number of the degrees of freedom to be actuated which is limited to five as well as the limited operating range extending around the patient's body compared to the requirements common in automation engineering. Further, in automation engineering variable robots which are suited for different tasks and maneuvers and which can be adapted to different loads are frequently used. On the other hand, the magnetic field generator of compact design according to aspects of the present invention constitutes a constant load that is not varying. The device for robot-guided orientation of the magnetic field generator of compact design therefore always has the same load, whereas in automation engineering different and dynamically changing loads are usual.
In the robot-guided orientation of a magnetic field generator of compact design for the control of intracorporeal objects the requirements to precision, variability of tracking and load bearing as described in the foregoing are definitely lower compared to the requirements in automation engineering. Using a robot from automation engineering as a device for robot-guided orientation of a magnetic field generator of compact design for the control of intracorporeal objects thus has the basic drawback that the design of the robot arm more than meets the requirements of the use as device for robot-guided orientation of a magnetic field generator of compact design according to aspects of the present invention for the control of intracorporeal objects such that this constitutes a risk for the patient and the operators. The specifications of the actuating elements of such robot which was designed for automation engineering moreover permit impacts on the patient's body endangering the patient.
On principle, experts strive for reducing over-dimensioned devices by so called “down-sizing” or reducing their power so that they are just adapted to fulfill the functions they are meant for. In the present case, however, the requirements to the robot and the magnetic guiding device are opposed, namely to the effect that, on the one hand, they must not be a risk for the patient and/or the operators and, on the other hand, they have to be sufficiently robust to withstand a permanent manual (even inappropriate) handling with all odds in a practice or hospital. Therefore, simple “down-sizing” according to known examples would not lead to a satisfactory result.